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Inorganic Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
The cements cited above are all typically derived from Portland cement. The following are non-Portland cements: Calcium-aluminate cement has a much higher percentage of alumina than does Portland cement. Furthermore, the active ingredients are lime, CaO, and alumina. In Europe, it is called melted or fused cement. In the United State, it is manufactured under the trade name Lumnite. Its major advantage is its rapidity of hardening, developing high strength within a day or two.Magnesia cement is largely composed of magnesium oxide (MgO). In practice, magnesium oxide is mixed with fillers and rocks and an aqueous solution of magnesium chloride. This cement sets up (hardens) within 2–8 h and is employed for flooring in special circumstances.Gypsum, or hydrated calcium sulfate (CaSO4 ⋅ 2H2O), serves as the basis of a number of products, including plaster of Paris (also known as molding plaster, wall plaster, and finishing plaster). The ease with which plaster of Paris and other gypsum cements can be mixed and cast (applied) and the rapidity with which they harden contribute to their importance in the construction field as a major component for plaster wall boards. Plaster of Paris' lack of shrinkage in hardening accounts for its use in casts. Plaster of Paris is also employed as dental plaster and pottery plaster, and as molds for decorative figures. Unlike Portland cement, plaster of Paris requires only about 20% water and dries to the touch in 30–60 min giving maximum strength after 2–3 days. Portland cement requires several weeks to reach maximum strength.
A State-Of-The-Art Review on Materials Production and Processing Using Solar Energy
Published in Mineral Processing and Extractive Metallurgy Review, 2023
It is not possible to conclude this section without referring to the calcium aluminate synthesis. Abdurakhmanov, Paizullakhanov, and Akhadov (2012) were the first in investigating with these compounds using solar energy. They did so with the aim of using calcium aluminates with impurities of neodymium and strontium based on the luminescence of these materials to obtain light-generating material. However, it was not until the research of Fernández-González et al. (2018d) when the synthesis of calcium aluminate cements using concentrated solar energy was proposed. Calcium aluminate cements are the most important type of cements after the Portland cement that are characterized by the rapid hardening, resistance to high temperatures, to temperature changes, to chemical attack and to impact and abrasion. Nevertheless, this type of cement, as opposed to Portland cement, is expensive due to the control of the impurities and the high temperature required for its synthesis. Fernández-González et al. (2018d) did preliminary research in the Odeillo solar furnace oriented to the synthesis of the high alumina calcium aluminate cement and observed that the habitual phases of calcium aluminate cements were obtained at the end of the process with certain heterogeneity due to the experimental conditions (static tests). Anyway, these researchers demonstrated that concentrated solar energy is a suitable candidate to obtain this kind of cements, although further research is needed for the implementation of this process at larger scale.
Facile auto-combustion synthesis of calcium aluminate nanoparticles for efficient removal of Ni(II) and As(III) ions from wastewater
Published in Environmental Technology, 2023
Hossam S. Jahin, Magdy I. Kandil, Mostafa Y. Nassar
Calcium aluminate (CA) is widely used in different applications such as cement and steel industry because of its relatively low density, hardness, straightness, etc. [24–27]. Calcium aluminate (CA) was also used as a material for bone graft application owing to its singular combination of physical and mechanical, bioactive, and biocompatible properties [28,29]. It is also utilized as optical ceramics, catalyst support, flame detectors, dental cement, and advanced ceramics [30–37]. Calcium aluminates (CA) powders were synthesized via different methods like solid-state reactions [38], sol–gel [39], polymeric precursor processes [40], and high-energy ball milling [41], spray-drying [42], Pechini method [43,44], and combustion method [45,46]. It is worth mentioning that the auto-combustion method can be employed for the synthesis of simple and complex inorganic materials [47,48]. This is owing to the simplicity, scalability, low cost, short time, and energy saving of the auto-combustion synthesis. Recently, calcium aluminate nanoparticles were used for the removal of dyes and pigments from industrial effluents and wastewater by the adsorption process [49,50]. To the best of our knowledge, no such research was reported on the preparation of monoclinic CaAl2O4 using a simple auto-combustion method, followed by the application of monoclinic CaAl2O4 as an adsorbent for the removal of heavy metals from wastewater.
Alkali-silica reaction in calcium aluminate cement mortars induced by deicing salts solutions
Published in Road Materials and Pavement Design, 2022
Calcium aluminate cement (CAC) is much different from Portland cement in terms of phase composition of both clinker phases, as well as hydration products. Portland cement is mainly composed of calcium silicates, while CAC consists mainly of calcium aluminates. Portland cement hydration products are C-S-H phase, calcium hydroxide and calcium sulphoaluminates: monosulphate and ettringite. In CAC hardened paste, among hydration products, there are hydrated calcium aluminates (hexagonal or/and regular) and aluminium hydroxide. From the point of view of ASR, the main difference is the pH of the pore solution. In the case of Portland cement hardened paste, pH is usually within the range 13–14, with hydroxyl ions concentrations within the range 0.2–1.0 moles/dm3 depending on the water/cement ratio, age and cement composition (Glasser, 1992; Barneyback & Diamond, 1981; Page & Vennesland, 1983). In the case of CAC, pH is usually within the range from 11.5 to 12.5 depending on the age of the samples, especially if the conversion process took place, with hydroxyl ion concentration up to 0.05 moles/dm3 (Berra et. al., 1995; Taylor, 1997; Ideker et al., 2019). It shows that the difference is substantial. This is probably the reason why ASR in CAC-based materials has not been thoroughly investigated. However, CAC mortars and concretes are used as repairing materials in situations, when rapid hardening is needed, for example for airfield or road pavement restoration. Applied in such places, hardened material may be subjected to the action of deicers. As mentioned before, ASR caused by external alkalis originating from deicing solutions causes severe deteriorations of Portland cement-based structures. The action of concentrated salt solutions is even more severe compared to the corresponding hydroxide solution. It suggests that it should be investigated in a more detailed way if there is no corrosion of that type in case of CAC-based materials. The only one, at least known for Authors’ work in that area was reported by Thomas and Hayman (2011). The work was devoted to the action of seawater and deicers on CAC mortars and concretes. However, Authors published preliminary results of tests on the potential of ASR in CAC mortars containing reactive sand stored in 6M commercial potassium acetate solution. In the case of investigated sand, no significant expansion was found for samples tested according to a modified ASTM C1260 accelerated test.